Method of and apparatus for electrically producing sound



' V 1,640,140 Aug.23,1927' T. BODDE' v METHOD OF AND APPARATUS FOR ELECTRIGALLY PRODUCING SOUND Original Filed Jan. 1'7. 192:

v mmw nw INVENTOR T/lfaamei Z7000:

ATTORNEYJ atented Aug. 23,1927.

UNITED STATES PATENT OFF I C E I THEODORE BODDE, OF NIAGARA FALLS, NEW YORK.

-.'IMEE'.EIHIOD OF AND APPARATUS FOR ELECTRIGALLY PRODUCING SOUND.v

Application filed January 17, 1923, Serial No. 613,273. Renewed January 7, 1927.

This invention relates to a method of and apparatus for electrically producing sound, and more particularly to a method of and apparatus for transforming sound waves or impulses into corresponding current pulsations or impulses by the action of an electron discharge tube or valve.

It is known, as'described in the article by Albert W. Hull in the Journal of the American Institute of Electrical Engineers of September, 1921, that the electron stream or current between the electrodes of a vacuum tube or'electron discharge valve may be controlled by means of a magnetic field. In the action of these magnetically controlled valves, if a constant voltage is impressed between the cathode and anode, the current that flows through the tube, that is, the electron stream that discharges trom the cathode by'a magnetic field having a strength less than a certain critical value, is reduced to zero if the magnetic field is increased beyond that value; and thus by changing the strength of the magnetic field to magnitudes below or above a critical amount, the cur: rent across the electrodes and hence the current in a working circuit connected to the electrodes may be respectively established U5 or extinguished. I have discovered that this phenomenon or property of magnetic con trol of the electron emission of the tube or valve may be utilized for eitecting the transformation of. sound vibrations or impulses into corresponding electrical impulses for sound production and transmission, and that the tube or valve may be so constructed or designed as to permit of accomplishing this result; and a prime desideratum ot'my present invention comprehends the provision of a method of and apparatus for transforming or translating sound waves, vibrations or impulses into corresponding electrical waves or pulsationsby means of electron tubes or relays.

The magnetically controlled electron tube, or magnetron as it is termed, in. one of its most eificient forms comprises a vao'uous vessel of cylindrical configuration provided with an axially disposed filament which when heated to incandescence emits an electron stream which impinges upon a cylindrical plate or anode symmetrically surrounding the cathode, the stream being controlled by means of a magnetic field preferand impinges on the anode, while unaffected coil surrounding the tube or vessel. The paths of movement of the electrons projected from the cathode are found to be influenced by the magnetic field, the paths being ,bent or curved by the magnetic field, the degree of curvature imparted to the paths varying with the strength of the magnetic field. When the field is below" a critical value, the electron paths although curved still intersect the cylindrical anode, and since the electrons impinge on the anode, the current through the tube remains unafi'ected. When however the magnetic field exceeds the critical value, the electron paths are bent sufficiently to prevent the electrons from reaching the anode, and since the electrons do not impinge thereon, no current flows across the electrodes and the current in the working circuit connected to theelectrodes is accordingly extinguished, When the parts of the magnetron are symmetrically arranged, the

current may be abruptly changed from the maximum to zero value, the transition from a closed to an open circuit being, however, not abrupt where there is a lack of symmetry. I have discovered that when the magnetron is subjected to mechanical vibrations, a relative vibration between thec'athode and the anode is produced, the cathode pended in space stationary with respect to the vibrating anode, and as a result not only is a dis-symmetry produced which permits of more gradual changes or variations in the electron stream-whenthe magnetic field is at or about the critical point, but when the magnetron construction is modified as will appear hereinafter, variations in the current in the working circuit are obtainable corresponding in magnitude and frequency to. the vibrations to which the tube is subjected, the magnetron being thus rendered serviceable and adaptable for translating sound vibrations into sound producing electrical pulsations. I

To the accomplishment of the foregoing and such other objects as may hereinafter appear, my invention consists in the elements and their relation one to the other, as hereinafter particularly described and sought to be defined in the claims, reference being had to the accompanying drawings which show a preferred embodiment of my ably produced by an energized solenoid orapplied to a transmitter,

.or filament, due to its inertia, remaining susr in an opening or Fig. 2 is an end view thereof,

Fig. 3 is a graphical view showing the electrical characteristics of the magnetron and the manner of adjusting the magnetic field thereof, and

Figs. 1 and 5 are diagrammatic views depicting the principles or theory underlying the invention.

Referring now more in detail to the drawings and more particularly to Figs. 1 and 2 thereof, the magnetically controlled valve or magnetron generally designated as M is shown to comprise the vacuous vessel or tube 10 provided with the cathode in the form of a straight filament 11 arranged axially of the tube, and an anode 12, the said anode comprising a section or portion of a surface of a cylinder as will be detailed further hereinafter, the filament being provided with the sealed terminals 13 and 14 and the anode being provided with the sealed terminal 15; and encircling the tube 10 symmetrically with the cathode and anode there is provided' the solenoid 16 for producing a controlling magnetic field.

For heating the filament to incandescence a closed circuit is provided which includes the battery 17, the opposite poles of which are connected to the filament terminals 13 and 14 by means of the conductors 18 and 19. As is well known, upon heating the filament 11 by means of this closed circuit, there will be an emission of electrons from the filament 11 to the anode 12, and upon closing a working circuit connected to the anode and cathode a current will be established therethrough.

For energizing the solenoid'16, the .same may be connected to a source of current which may be the battery 17 by means of a circuit comprising the conductor 20, the coil of solenoid 16, conductor 21, and rheostat 22, the rheostat being employed for pre-- determining the degree of energization of the solenoid and hence the magnitude of the magnetic field.

As above mentioned, if the electron tube be subjected to a magneticfield normal or at right angles to the electron paths and below a predetermined amount, the emission of the electrons from the cathode and the inn-- pinging of these electrons on the anode of the tube will be uninterrupted and unhindered, and that if the tube be subjected to a magnetic field beyond such predetermined amount, the electrons will be diverted and prevented from reaching the anode, resulting extinguishment of the tube circuit and the opening of the working circuit controlled thereby. The graphical representation of this phenomenon is shown in Fig. 3, in which the strength of the magnetic field is represented by the abscissae, and the strength of the current flowing between the cathode and anode is represented ures along the curve DE being more or less abrupt as the parts of the magnetron are more or less symmetrical in arrangement.

For the purpose of transforming vibrations such as sound vibrations into corresponding electrical pulsations, the magnetron of my present invention is mounted on a vibratable member which may be set into vibration in accordance with sound waves impinging thereon, the said vibratable member comprising for example a sounding board or a d1aphragm of a transmitter. This is shown for example in Figs. 1 and 2 of the drawings, and referring to these figuresthe magnetron is shown mounted for movement with a diaphragm 23 which is associated with the mouthpiece 24, the magnetron being preferably bodily mounted on and carried by the diaphragm 23 by means of the supporting element 25. Also preferably in order to minimize the weight carried by the diaphragm 23, the tube 10 alone is carried by the diaphragm, the solenoid 16 being arranged so as to be maintained in a relatively stationary condition during vibration of the tube. With this construction as the diaphragm and the tube are set into vibratory motion, the mode 12 is moved relatively to the cathode or filament 11, the latter remaining suspended in stationary position due to its inertia. In order to heighten this inertia effect, the cathode 11 may be weighted at its ends, as by means of the small weights 26. When the tube is set into vibratory motion and when the solenoid 16 effects variations in the electron stream reaching the anode, which variations are proportional in magnitude or amplitude and frequency to the oscillations or vibrations impressed on the tube. By connecting across the electrodes a receiving circuit which may include the receiver 27, battery 28, and conductors 29 and 30, it will be apparent that the variations in the electron stream will produce corresponding sound producing variations in the current of the working or receiving circuit.

That the change in the electric current or stream varies proportionally with the impressed mechanical vibrations of the tube system will appear from a consideration of Figs. 3 to 5 of the drawings. In these figl have a e p ed to d p ct in a diagrammatic fashion the underlying theory of theinvention, and I desire it to be understood that although this theory I believe to be properly explanatory of the phenomenon or the behaviour of theapparatus, the theory" is presented by way of explanation only, and not by way of limitation. 'VVhen the solenoid 16 is energized to produce a magnetic field having a value at or about the critical value as represented for example by the asterisk on the curve represented in Fig. 3, the current in the tube is at the transition point, and the average electron path may be represented by the curve 00 (Fig. 4),

the electron path being tangent to the anode 12. This, however, is only the average path,

and due to such factors as the physical dimension of the filament, the lack of complete symmetry of the parts, etc., the electrons'are projected from the cathode in a plurality of proximate paths such for example as the paths w, 3 and (a, .the electrons in the path a impinging on the anode, and the electrons in the path y circling about in the closed path, as shown, without touching the anode. When the tube is vibrated, however, more or less of the electrons reach the anode according to the position of the tube and attached anode with respect to the. relatively stationary cathode. This is depicted in Fig. 5 of the drawings, which shows the diaphragm 23, tube 10 and anode 12 in three successive positions F, G and H, the anode in .position 12F embracing the electron paths w, "y and z, the anode in position 12G embracing the paths as and a, and the anode in position 12H embracing only the path a. It will therefore be evident that the total electron stream emanating from the filament .and impinging against the cylindrical anode surface varies progressively with and in pro portion to the vibratory motion of the tube.

The anode 12, as heretofore mentioned, is a section or a part of a cylinder, and more particularly a cylinder with. one side cut away, and in the preferred form comprises a quadrant of acylinder. The cylindrical anode, asdistinguished from known mag-.

'netrons, is cut away on one side for the reason that if a full cylinder is employed, any variation in the electron current on one side produced by the vibrations would be neutralized or compensated for by an equal and opposite variation on the opposite side, producing" a net result of no variation in the working circuit. With one side of the anode; however, removed the electron stream variations on one side of the cylinder produces the current in the working circuit'as desired.

The use and operation of the apparatus and the practice of the method will in the main be fully apparent from the above detailed description thereof. It will be further apparent that although I have shown my invention applied on a diaphragm or sounding board directly responsive to sound such as speech to electrically produce sound producing variations in an electric current, this application of the inventionhas been given merely by way of example, and that other applications will beobvious to those skilled in the art. For example, the magnetron may be subjected to vibrations of a mechanicalvibrating system such as employed in phonograph sound reproduction for the transmission of speech. It will further be seen that with the provision of the apparatus described, an extremely sensitive transmitter is obtained which in addition to its sensitiveness is entirely free from the unavoidable secondary current variations which occur in known transmitters.

-VVhile I have shown my device in the preferred form, it will be obvious that many changes and modifications may be made in the structure disclosed without vdeparting fromthe" spirit of the invention, defined in the following claims.

I claim: 1 i 1. The method of transforming sound impulses into corresponding electrical impulses which consists in subjecting the electron stream of an electron discharge device to a magnetic field such that the electron stream emanating from the cathode of the device is caused to move substantially tangentially to the anode of the device and in setting up relative vibration between the cathode and anode responsive to sound im- 100 pulses whereby variations in the electron stream impinging upon or touching the anode are produced in correspondence with the sound impulses.

2. The method of transforming sound im- 105 pulses into corresponding electrical impulses which consists in subjecting the electron stream of an electron discharge device to a magnetic field such that the electron stream emanating from the cathode of the 110 device is caused to move substantially tangentially to the anode of the device and in subjecting the device to vibrations set up in response to sound impulses for producing variations in the electron stream impinging 115 upon or touching the anode in correspondence with the sound impulses.

3. The method of transforming sound impulses into corresponding electrical impulses which consists in producing in an 1 electron discharge device a curved electron stream moving from the cathode of the device to an electrode which is disposed substantially tangent to the electron stream and in setting up relative vibration between the 12 cathode and electrode .responsive to sound impulses-whereby variations in the electron stream impinging upon or touching the electrode are produced in correspondence with the sound impulses,

4. The method of transforming sound impulses into corresponding electrical impulses which consists in producing in an electron discharge device a curved electron stream moving from the cathode of the device to an electrode which is disposed substantially tangent to the electron stream and in subjecting the device to vibrations set up in response to sound impulses for producing variations in the electron stream impinging on or touching the electrode in correspondence with the sound impulses.

5. The method of transforming sound impulses into correspondin electrical impulses which consists in subjecting the electron stream moving from the cathode to the anode of an electron discharge device to a magnetic field which is normal to the paths of the electrons and which is of such magnitude as to cause the electron stream to move substantially tangentially to the anode and in setting 11 relative vibrations between the cathode ant anode responsive to sound impulses whereby variations in the electron stream impinging upon or touching the anode are produced in correspondence with the sound impulses.

6. In the method of producing sound by variations of an electrical current, the step of effecting relative vibrations between the cathode and the anode of an electron discharge device in which the electron stream is controlled by a magnetic field whereby variations in the electron stream or current impinging on the anode are produced.

7. An apparatus for producing sound by variations of an electrical current comprising an electron discharge device having a cathode and an anode, means for causing the electron stream emanating from the cathode to move substantially tangentially to the anode and means for effecting a relative vibration between the cathode and the anode responsive to sound impulses for producing variations in the electron stream impinging upon or touching the anode 1n correspondence with the sound impulses.

8. An apparatus for producing sound by -variations of an electrical current comprising an electron discharge device having a cathode and an anode, means for causing the electron stream emanating from the cathode to move substantially tangentially to the anode and means for effecting vibrations of the device in response to sound impulses to produce variations in the electron stream impinging upon or touching the anode in correspondence with the sound impulses.

9. An apparatus for producing sound by variations of an electrical current comprising an electron discharge device having a cathode and an anode, means for curving the stream of electrons emanating from the cathode, the surface of the anode being arranged tangent to said stream, and vibratable means for varying the touching distance between the anode surface and the body of the electron stream.

10. An apparatus for producing sound by variations of an electrical current comprising an electron discharge device having a cathode and an anode, means for producing a magnetic field effective for causing the electron stream emanating from the cathode to move substantially tangentially to the anode andmeans for effecting a relative vibration between the cathode and the anode responsive to sound impulses for producing variations in the electron stream impinging upon or touching the anode in correspondence with the sound impulses.

11. An apparatus for producing sound by variations of an electrical current comprising an electron discharge device having a cathode and an anode, means for producing a magnetic field which is normal to the paths of the electrons emanating from the cathode and which is of such a magnitude as to cause te electron stream to move substantially tangentially to the anode and means for effecting a relative vibration between the cathode and the anode responsive to sound impulses for producing variations in the electron stream impinging upon or touching the anode in correspondence with the sound impulses.

12. An apparatus for producing sound by variations of an electrical current comprising an electron discharge device having a cathode and an anode, means for producing a magnetic field for curving the stream of electrons emanating from the cathode, the surface of the anode being arranged tangent to said stream, and vibratable means for varying the touching distance between the anode surface and the body of the electron stream.

13. An apparatus for producing sound by variations of an electrical current comprislng an electron discharge device having .a cathode, an anode, and a means producing an electron discharge controlling manetic field, .and means for effecting relative vibrations between the cathode and anode to produce variations in .the electron stream impinging on the anode.

14. An apparatus for producing sound by variations of an electrical current comprising an electron discharge device having a cathode, an anode and a means producing an electron discharge controlling magnetic field which is at or about the critical point, and means for effecting relative vibrations between the cathode and anode to produce variations in the electron stream impinging on the anode.

15. An apparatus for producing sound by variations of an electrical current comprising an element vibratable in response to sound impulses, an electron discharge device including a cathode and an anode mounted for producing relative movement between the cathode and anode upon vibration of said elements, and relatively stationary means for producing a magnetic field for controlling the electron discharge of the device.

16. An apparatus for producing'sound by variations of an electrical current, comprising an element vibratable in response to sound impulses, an electron discharge device includin a cathode and an anode mounted for pro ucing relative movement between the cathode and anode upon vibration of said elements, and .relatively stationary means for producing a magnetic field normal to the paths of the electrons for controlling the electron discharge of the device.

17. A transmitter com rising a diaphragm or the like, an electron discharge device having a cathode and an anode mounted on the diaphragm, and a magnetizing coil surrounding the device and arranged to be held stationary during vibration of the diaphragm and the device.

18. An electron discharge device comprising a cathode, an anode, means for producing an electron discharge controlling magnetic field normal to the paths of the electron, the said anode being arranged to only partially surround the cathode whereby when relative motion between cathode and anode is eflected a variation of the electron stream im inging on the anode will be produced.

gi ed at Niagara Falls, in the county of Niagara and State of New York. this 13th day of January A. D. 1928.

THEODORE BODDE. 

